2-Methyl-3-[2-methyl-5-isopropenyl-cyclopent-1en-1-yl]-propyl ester derivatives are compounds of particular interest for perfumery, see U.S. Pat. Nos. 3,937,723 and 3,978,009. They develop a variety of odoriferous notes ranging from green to fruity or flowery notes and, accordingly, they find a very broad field of use in various fine and technical perfume compositions.
A process for their preparation - see above cited U.S. patents - consists in thermally cyclising 2,6-dimethyl-oct-2-en-7-yn-6-ol, treating the thus obtained product with ethyoxyprop-1-ene to yield an aldehydic derivative, reducing the obtained aldehyde to the corresponding primary alcohol and eventually acylating the said alcohol. The said process is illustrated by the herinbelow reaction scheme. ##STR1## Alk = alkyl radical
The above said process, which sofar has been successfully applied to industrial scale preparations, suffers however of certain practical disadvantages. The reaction between the cyclic tertiary alcohol and ethoxy-prop-1-ene, in fact, is very often accompanied by concomitant polymerizations, which consequently reduce the yields of the end-product and increase the technical difficulty in the final purification step. A novel, more satisfactory approach for the preparation of the aforementioned ester derivatives was therefore the goal of further investigations.